Were contracted under subcontract option A.
If clause X1 does not apply would you be entitled to claim price fluctuations which are a result of delays from the Contractor as a compensation event?
The assessment is the affect on Defined Cost. Although you couldn’t apply an X1 ‘price fluctuation’ adjustment, per se, if you have genuine grounds to believe that there is an increase in Defined Cost directly due to the time delays caused by the CE, then I believe that would be a genuine assessment within a quotation. If the situation is not so clearly quantifiable, then perhaps consider including a risk allowance calculation assessment.
X1 is specifically about “inflation” rather than any price fluctuations. But not withstanding that, any compensation event that you are assessing you are basing it on prices/risk that you now know about. Therefore if the price for a particularly item is now more expensive than you priced for at tender stage, whilst for the contract works that would be your risk but any CE you can now price at the rate you know it would be - as per definition of Defined Cost.
You only use activity schedule rates under option A by agreement to assess a CE, and even then on a case by case basis. The activity schedule rate is largely irrelevant at that stage (unless you both agree otherwise).